一个关于字符串打印到GraphicsContext上的有关问题

+ (void)generatePDFByImg:(UIImage *)img andText:(NSString *)text
{
    //    self.toolBar.hidden = YES;
    //    NSString *text = @"puma are large cat-like animals which are found in Americ";
    
    CGSize pdfSize;
    pdfSize.height = 460;
    pdfSize.width = 320;
    
    UIGraphicsBeginImageContext([[UIScreen mainScreen] bounds].size);
    //    [self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
    //  UIImage *pdfImage = UIGraphicsGetImageFromCurrentImageContext();
    //    UIGraphicsEndImageContext();
    //    self.iiimagev.image = pdfImage;
    
    //    UIImage *pdfImage = [UIImage imageNamed:@"10074136.jpg"];
    
    NSMutableData* outputData = [[NSMutableData alloc] init];
    CGDataConsumerRef dataConsumer = CGDataConsumerCreateWithCFData((__bridge CFMutableDataRef)outputData);
    CFMutableDictionaryRef attrDictionary = NULL;
    attrDictionary = CFDictionaryCreateMutable(NULL, 0, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
    
    CGContextRef pdfContext = CGPDFContextCreate(dataConsumer, NULL, attrDictionary);
    CFRelease(dataConsumer);
    CFRelease(attrDictionary);
    UIImage* myUIImage = img;
    CGImageRef pageImage = [myUIImage CGImage];
    CGPDFContextBeginPage(pdfContext, NULL);
    NSLog(@"[myUIImage size].width = %f",[myUIImage size].width);
    NSLog(@"[myUIImage size].height = %f",[myUIImage size].height);
    CGContextDrawImage(pdfContext, CGRectMake(0,[[UIScreen mainScreen] bounds].size.height,([myUIImage size].width)*2 , ([myUIImage size].height)*2), pageImage);
  //  NSLog(@"[myUIImage size].width = %f",[myUIImage size].width);
  //  NSLog(@"[myUIImage size].height = %f",[myUIImage size].height);